Deliberate design of an acentric diamondoid metal-organic network

Reaction of 2.5-dicarboxy-1-methylpyridinium (DCMP) chloride and Zn(NO3)2·6H2O in the presence of NaHCO3 in water gave an expected acentric diamondoid network [Zn(DCMP)2] with a three-fold interpenetration. With long Zn–Zn separations, very large cavities are formed within each diamondoid network with high propensity to interpenetration, which makes it show a promising non-linear optical property with SHG efficiency approximately 7 times higher than that of potassium dihydrogen phosphate (KDP). The design strategy of ligand through methylation of the corresponding pyrdinecarboxylic acid can be extended to other widely used carboxylic acids, more importantly, to lead to an unsymmetric bifunctional bridging ligand, which is essential for generating polar solids.